Sometimes you get the feeling that people visit threads, read the question, quickly scan the top voted answer, and then just throw another vote onto the pile. "Yeah, that's it", they seem to think.
But it can be really annoying when the top voted "answer" to your question is not the solution to the problem. Adding a comment isn't always enough - especially if the comment gets folded away.
Since it's at the top of the stack, it's likely to get pushed up further by drive-by-voters. Which is really irritating.
Perhaps the OP should be allowed to downvote any answer in a question he has posted back to 0, regardless of how many upvotes it gets.